东亚沙尘气候效应对地面温度日较差影响的数值模拟

Influence of dust aerosol on land surface diurnal temperature range over East Asia Simulated with the WRF-Chem model

地面温度日较差(DTR)作为重要天气和气候指标,反映昼夜温差极值,比平均气温对地表辐射收支的变化更敏感,对环境变化和气候异常具有重要参考价值。沙尘气溶胶的气候效应是影响岩石圈-大气-海洋系统的重要因子,但目前的研究较少涉及沙尘气溶胶对DTR的影响机制。基于WRF-Chem模式(Weather Research and Forecasting coupled with Chemistry)揭示2002—2005年沙尘气溶胶气候效应对东亚地面温度日较差的影响。结果表明:WRF-Chem模式可以很好体现东亚气象场和沙尘气溶胶的时空分布特征。沙尘气候效应导致东亚大陆大部分地区DTR减小,沙尘直接辐射效应在其中起决定性作用。在白天,沙尘直接辐射强迫加热大气、冷却地表,减小地面总净辐射而降低日最高温度,导致DTR减小。在中国青藏高原和东北部地区,沙尘气溶胶间接效应占主导地位,导致青藏高原地区积雪覆盖减少,东北地区云水含量减小,间接导致DTR增大。

As an important synoptic and climate index,diurnal temperature range(DTR)reflects the extreme temperature difference between day and night.Compared with average temperature,DTR is more sensitive to changes in surface radiation budget and has important reference value for environmental changes and climate anomalies.The physical process of dust aerosol and its climatic effect are important factors affecting the lithosphere-atmosphere-ocean system,but the influence of dust climate effects on DTR has not been studied.The study reveals the climatic impact of dust aerosol on DTR over East Asia during 2002-2005 based on the WRFChem model(Weather Research and Forecasting coupled with Chemistry).The results show that the WRF-Chem model can well reproduce the spatial-temporal distributions of meteorological field and dust aerosol over East Asia.The dust climate effect dominated by direct radiative forcing leads to the decrease of DTR in most parts of East Asia continent.During daytime,the direct radiative effect induced by dust heats the atmosphere and cools the surface,contributing to net surface radiation-cutting,thus further the decrease of the maximum Temperature and DTR.In contrast,an opposite variation tendency of DTR,primarily regulated by dust indirect effect,occurred over the Tibet Plateau and the northeast of China due to reduction of snow cover and liquid water path,respectively.